Temperature-dependent operation of GaInAsP/InP VCSELs

We present the results of our studies concerning the pulsed operation of a bulk GaInAsP/InP vertical cavity surface emitting laser (VCSEL). The device is tailored to emit at around 1.5 micrometers at room temperature. The structure has a 45-period n-doped GaInAsP/InP bottom Distributed Bragg Reflector (DBR), and a 4 period Si/Al2O3 dielectric top reflector defining a 3-(lambda) cavity. Electroluminescence from a 16micrometers diameter top window was measured in the pulsed injection mode. Spectral measurements were recorded in the temperature range between 125K and 240K. Lasing threshold current density has a broad minimum at temperatures between 170K-190K. In order to establish the relationship between the temperature dependence of the threshold current and the gain peak, we investigated the spectral dependence of edge and surface emission from optically pumped structures without the top reflector. Experimental result are compared with existing theories concerning the temperature dependence of threshold current.